Shaped inoculation means for iron casting melts

ABSTRACT

An inoculation body is cast or sintered with grains of a silicide in a matrix of a metal having a lower melting point than iron, such as aluminum, tin or zinc, in the shape of a main body having a flat bottom surface with a perpendicularly projecting peg or stem in the mid-portion of the bottom surface. The stem may be tapered slightly. Such an inoculation body is used by seating it on its flat bottom surface on a strainer grate core of a casting mold, with the stem or peg projection extending into a perforation of the strainer grate core. The flat bottom and the projection cooperate to maintain the inoculation body in its central position on the grate core during transportation of the mold to the pouring position, as well as during the pouring operation.

United States Patent 1 [111 3,881,937

Teufel [4 1 May 6, 1975 SHAPED INOCULATION MEANS FOR IRON CASTING MELTS[21] Appl. No.: 438,651

[30] Foreign Application Priority Data Feb. 27, 1973 Germany 2309654U.S. Cl 75/130 R; 75/58; 75/93 G Int. Cl C22c 37/02; C216 7/00, C22b9/12 Field of Search 75/130 R, 58, 93 G, 130 B References Cited UNITEDSTATES PATENTS S/l95l Tour 75/93 IT 7/1968 Robertson........ 75/]30 RPrimary Examiner-P. D. Rosenberg Attorney, Agent, or FirmFlynn &Frishauf {57] ABSTRACT An inoculation body is cast or sintered withgrains of a silicide in a matrix of a metal having a lower melting pointthan iron, such as aluminum, tin or zinc, in the shape of a main bodyhaving a flat bottom surface with a perpendicularly projecting peg orstem in the mid-portion of the bottom surface. The stem may be taperedslightly. Such an inoculation body is used by seating it on its flatbottom surface on a strainer grate core of a casting mold, with the stemor peg projection extending into a perforation of the strainer gratecore. The flat bottom and the projection cooperate to maintain theinoculation body in its central position on the grate core duringtransportation of the mold to the pouring position, as well as duringthe pouring operation.

4 Claims, 2 Drawing Figures SHAPED INOCULATION MEANS FOR IRON CASTINGMELTS This invention relates to means for inoculating iron casting meltswith ferrosilicon and similar seeding inoculants to improve the castingproperties of the melts. In particular the invention relates to theprovision of solid bodies containing the silicide additive in a form tobe taken up readily by the melt and dispersed therein shortly prior tosolidification.

It is known that the addition of an inoeulant such ferrosilicon duringthe casting process improves the quality of iron castings. The inoculantis dissolved in the melt and has a favorable influence on the progressof solidification of the melt.

The casting so treated freezes in the gray iron condition throughout,whereas in the case of casting without inoculation, especially when thewall thickness ratios are unfavorable, the formation of cementite takesplace. The latter situation is accompanied by a considerable reductionof the mechanical qualities of the casting. The amount of inoculant tobe added is related to the weight of the casting. Thus for a casting of30 kg, for instance, the addition of 30 g of inoculant is sufficient andadvantageous. lnoculation by adding to the melt at the time of castingis more favorable than when the inoculant is provided beforehand in thecasting ladle, since in the latter case the favorable influence on thecast iron structure falls off exponentially with time.

Ferrosilicon can be cast at a temperature of about 3,()O()C. Thepractice heretofore has been to shatter plates of ferrosilicon so cast.sort the fragments according to weight or size and provide the materialin this form to foundries. Thus if a foundryman should need 30 g ofinoculant for a particular casting, he would take a fragment of thatweight and place it on the strainer grate core in the gate system of thecasting mold shortly before the melt is poured.

This method of foundry production is very expensive, because obtainingthe necessary weight for the lumps of inoculant is more or less a matterof chance. Attempts to control the apportionment of the quantity offerrosilicon by providing powdered material typically agglomerated withan organic binder, have led to no satisfactory results, because ofirregularity in the rate of solution. The production of cast blocks offerrosilicon in the desired sizes is difficult and troublesome, becauseof the high melting point of ferrosilicon and the high surface tensionof the molten material. At the same time a surface oxidation of thisinoculant takes place which reduces the solution tension.

It is known from German published patent application DAS No. 1,508, l 74to provide an inoculant in tablet form made of granular ferrosilicon anda fusible organic binder as a matrix, and to introduce such a tablet inthe casting mold. It is also known, from Swiss Pat. Nos. 457.738 and465.78l to provide shaped inocula tion bodies of ferrosilicon orferrosilicon alloys that contain. either as impurities or as purposefuladditions, metals that melt at temperatures lower than the melting pointof iron, such as aluminum or magnesium, with the use of an inorganicmatrix-forming material such as molding sand or hardened water glass andto place these inoculation bodies as plates in core marks of the pouringor gate system used for casting. In the prior pa tent application ofJ.Zcllerer and E. W. Rath, Ser. No. 312,796, filed Dec. 7, W72, animproved inoculation body was disclosed utilizing metal melting at alower temperature than iron as the matrix material itself and disclosedthe utilization of such a body either by placing it before the castingprocess on a strainer grate core of appropriate size or by sintering theinoculation body material together with this strained grate core to forma single firmly bound body.

It is an object of the present invention, in the interest on the onehand of maintaining the proper position of the body and on the otherhand assuring that the inoculation process proceeds properly, to providea certain freedom of design and interchangeability in the uniting ofstrainer grate core and inoculation body (which is not present in thepreviously mentioned combined body produced by sintering the strainergrate core and inoculation body materials together) and nevertheless, toassure that when the structure consisting of strainer grate core andinoculation body is brought to the place of casting, that theinoculation body will maintain its proper position on the strainer gratecore so that the inoculation process will effectively take place.

SUBJECT MATTER OF THE PRESENT lNVENTlON Briefly, the inoculation body isprovided with a peg or stem that is insertable in a hole in the strainergrate core on which it is used. It is desirable and effective for thisprojection provided on the inoculation body to be cast onto theinoculation body in such a way that it projects out of a flat supportingsurface of the inoculation body.

This configuration has the advantage that the body provided with a stemor peg can be used within certain limits for strainer grate cores ofdiffering dimensions. The users of the improved casting process are not,in accordance with the present invention, either relegated to the use ofcombination bodies in which the core and inoculation material aresintered together or to sticking a rod or pin of inoculation material ofa particular shape where it will lodge in position. Such rods or pinsare no longer necessary. Manufacture, positioning and securing aresimplified and improved. The user is assured that the configurationprovided by the mounting of the inoculation body on the strainer gratecore will maintain its correct position when set into the casting moldand transported to the place of pouring on a roller conveyer, i.e. thatthe inoculation body cannot fall off or out of its central placement onthe strainer grate core. This provides a saving in labor and anincreased assurance of the correct operation of the inoculation.

The invention is further described by way of example with reference tothe accompanying drawings, in which:

FIG. I is a cross-section of a casting mold and gate system with aninoculation body with a positioning stem in accordance with theinvention, and

FIG. 2 is a side elevation view on a larger scale of the inoculationbody itself with its positioning stem.

The casting mold shown in FIG. 1 consists of an upper mold and a lowermold, both shown partly broken away, each with one channel. The uppermold body has the pouring basin 1 and the reaction chamber 2. The lowermold body contains the collecting chamber 3, in the inlet to which isseated a perforated strainer grate core 4.

In the central perforation of the strainer grate core 4 is inserted thestem or peg 6 of the inoculation body 5.

The main part of this body itself has a flat lower sup porting surface 7that surrounds the stem or peg 6. When the inoculation body iscylindrical as shown in FIGS. 1 and 2, the supporting surface 7 is offlat annular shape. The provision of this supporting surface enables theinoculation body to be seated firmly on the surface of the strainergrate core 4. The insertion peg 6 cast onto the inoculation bodyprojecting into the perforation of the strainer grate core 4 may be veryslightly tapered towards its extremity, as shown in FIG. 2. Likewise theupper part of the body 5, above the plane of the line 8 of FIG. 2 may beslightly tapered towards the top.

The stem or peg 6 is preferably cast at the same time and of the samematerial as the inoculation body when it is made by flooding theferrosilicon grains with aluminum, in a mold, or by sintering theferrosilicon grains with aluminum powder in a chill mold. Alternatively,it could be cast on later with the same or a compatible material in aseparate operation.

In practice the casting melt is poured into the mold through thestrainer grate core and around the inoculation body. The aluminum orother light metal (e.g. tin, zinc) component is quickly released bymelting and floats on the surface of the melt. The ferrosilicon grainsthus freed with their surfaces in reactive condition are quickly andfully dissolved by the iron. so that the intended inoculation effect isobtained to the highest possible degree.

Although the invention has been described with reference to a particularembodiment, it will be under stood that variations and modifications maybe made within the inventive concept.

I claim:

1. Shaped body inoculation means for introducing a silicide additiveinto an iron casting melt consisting of grains of said silicide embeddedin a metal having a melting point lower than that of iron and shaped ina main body and peg-like projection means extending outward therefromfor positioning said body on a perforated strainer grate core with saidprojection in a perforation of said core.

2. Shaped body inoculation means as defined in claim 1, in which saidmain body has a flat seating surface surrounding said projection andsaid projection extends outward in a direction perpendicular thereto,whereby said body may be seated by said flat surface resting on saidgrate core when said body is positioned by said projection thereon asaforesaid.

3. Shaped body inoculation means as defined in claim 2, in which saidmain body and said projection are of the same material having the grainsof said silicide homogeneously dispersed in the bulk of said main bodyand projection in the said metal in which they are em' bedded.

4. Shaped body inoculation means as defined in claim 2, in which saidprojection is tapered down to a slightly smaller cross-section at itsextremity from a larger cross-section at its base where it adjoins saidmain body.

1. SHAPED BODY INOCULATION MEANS FOR INTRODUCING A SILICIDE ADDITIVEINTO AN IRON CASTING MELT CONSITING OF GRAINS OF SAID SILICIDE EMBEDDEDIN A METAL HAVING A MELTING POINT LOWER THAN THAT OF IRON AND SHAPED INA MAIN BODY AND PEG-LIKE PROJECTION MEANS EXTENDING OUTWARD THEREFROMFOR POSITIONING SAID BODY ON A PERFORATED STRAINER GRATE CORE WITH SAIDPROJECTION IN A PERFORATION OF SAID CORE.
 2. Shaped body inoculationmeans as defined in claim 1, in which said main body has a flat seatingsurface surrounding said projection and said projection extends outwardin a direction perpendicular thereto, whereby said body may be seated bysaid flat surface resting on said grate core when said body ispositioned by said projection thereon as aforesaid.
 3. Shaped bodyinoculation means as defined in claim 2, in which said main body andsaid projection are of the same material having the grains of saidsilicide homogeneously dispersed in the bulk of said main body andprojection in the said metal in which they are embedded.
 4. Shaped bodyinoculation means as defined in claim 2, in which said projection istapered down to a slightly smaller cross-section at its extremity from alarger cross-section at its base where it adjoins said main body.